1. Field of the Invention
The present invention relates to a bis(methoxymethyl)biphenyl useful as a starting material for a phenol novolak resin and an epoxy resin modifier, any mixtures of six isomers thereof, and processes for producing the same.
The present invention also relates to a novel phenol novolak condensate obtainable from a reaction between isomers of a bis(methoxymethyl)biphenyl or a mixture thereof and a phenol compound. This condensate is useful as a curing agent for an epoxy resin and a starting material for an epoxidized novolak resin, in addition to being useful for a thermosetting resin with a cross-linking agent such as hexamethylenetetramine.
2. Description of the Related Art
As an aromatic bis(methoxymethyl) derivative, there has been known in the past 1,4-bis(methoxymethyl)benzene. Phenol resins using this are disclosed in Japanese Examined Patent Publication (Kokoku) No. 47-13782, Japanese Examined Patent Publication (Kokoku) No. 47-15111, and Japanese Examined Patent Publication (Kokoku) No. 48-10960. However, a bis(methoxymethyl)biphenyl has not been known. Japanese Examined Patent Publication (Kokoku) No. 47-13782 and Japanese Examined Patent Publication (Kokoku) No. 47-15111 disclose that a bis(alkoxymethyl) biphenyl can be used for the production of phenol polymers. However, there were no examples of experiments actually using it for a phenol polymer.
Further, DE-2648701 discloses an example of the use of a 4,4'-isomer of bis(methoxymethyl)biphenyl as a component of a flame retardent improvement agent for polyvinyl chloride and an example of the synthesis of the same. According to this process, biphenyl is chloromethylated the biphenyl, followed by reacting with methanol in the presence of potassium hydroxide, then synthesizing bis(methoxymethyl)biphenyl. Since a 4,4'-isomer is produced at the chloromethylation stage, however, it is extremely difficult to synthesize a bis(methoxymethyl)biphenyl other than the 4,4'-isomer. Further, it is relatively easy to introduce a single chloromethyl group into biphenyl, but introducing two chloromethyl groups is hard. According to this reference, the reaction takes a long period of about 20 hours and further has a yield of about 60%.
Accordingly, a process for the production of a novel bis(methoxymethyl)biphenyl other than the 4,4'-isomer, and an industrially acceptable process for producing the same with a good yield of bis(methoxymethyl)biphenyl, including the 4,4'-isomer, have been sought.
Phenol novolak resins have been used as materials for brake pads etc. mixed with asbestos fibers and other fibrous fillers due to their low wearability, their good dimensional stability at high temperatures, and their good bonding ability, etc., but they have not necessarily been satisfactory in terms of heat resistance, etc.
Further, novolak epoxy resins obtained from a reaction of epoxy compounds with the phenol novolak resins, in particular, cresol novolak type epoxy resins, are inexpensive and are excellent in productivity, and therefore, these resins are widely used for semiconductor packages. These materials, however, sometimes have suffered from cracking, known as the "popcorn phenomenon," which accompanies rapid vaporization and expansion of the absorbed moisture at the time of solder reflow. Accordingly, a material having a low hygroscopicity and superior heat resistance has been sought. Improvement of the hygroscopicity and heat resistance is desired for the phenol novolak resins used as the curing agents of the epoxy resins as well.
As a method for solving the problem of heat resistance, it has been proposed in Japanese Examined Patent Publication (Kokoku) No. 47-13782, Japanese Examined Patent Publication (Kokoku) No. 47-15111, and Japanese Examined Patent Publication (Kokoku) No. 48-10960 to replace part or all of the formaldehyde with 1,4-bis(methoxymethyl)benzene or, in Japanese Unexamined Patent Publication (Kokai) No. 4-110317, it is proposed that bis(hydroxymethyl)benzene be reacted with a phenol compound to give a phenol polycondensate.
However, the epoxidated phenol resin obtained by this method is insufficient in heat resistance and is insufficient in improvement of hygroscopicity as well.
Further, a method for reducing the hygroscopicity property by an addition reaction of divinylbenzene instead of formaldehyde, with the phenol, followed by reacting with the epoxy compound has been disclosed in Japanese Unexamined Patent Publication (Kokai) No. 5-78457, but the result is not sufficient in terms of strength and low hygroscopicity.
Japanese Examined Patent Publication (Kokoku) No. 47-13782, Japanese Examined Patent Publication (Kokoku) No. 47-15111, and Japanese Unexamined Patent Publication (Kokai) No. 4-110317 disclose that it is possible to use bis(methoxymethyl) biphenyl or bis(hydroxymethyl)biphenyl to obtain a phenol polycondensate, but these publications make no specific disclosure of the invention of this application.
Further, Japanese Unexamined Patent Publication (Kokai) No. 5-117350 discloses a specific example of a 2:1 condensate of 2 molecules of phenol and 1 molecule of 4,4'-di(2-hydroxy-2-propyl)biphenyl. However, since this low molecular phenolic compound is crystalline and has a low melt viscosity, there is a problem that this compound is not easy to handle due to its large flowability during molding. On the other hand, this reference discloses that it is possible to use 4,4'-bis(methoxymethyl)biphenyl, but it does not specifically disclose the invention of this application.